> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/sql-statements/geometry-constructors/polygon-properties/st_exteriorring.md).

# ST\_ExteriorRing

## Syntax

```bnf
ST_ExteriorRing(poly)
ExteriorRing(poly)
```

## Description

Returns the exterior ring of the Polygon value `poly` as a LineString.

`ST_ExteriorRing()` and `ExteriorRing()` are synonyms.

## Examples

```sql
SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';

SELECT AsText(ExteriorRing(GeomFromText(@poly)));
+-------------------------------------------+
| AsText(ExteriorRing(GeomFromText(@poly))) |
+-------------------------------------------+
| LINESTRING(0 0,0 3,3 3,3 0,0 0)           |
+-------------------------------------------+
```

<sub>*This page is licensed: GPLv2, originally from*</sub> [<sub>*fill\_help\_tables.sql*</sub>](https://github.com/MariaDB/server/blob/main/scripts/fill_help_tables.sql)

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